1. Field of the Invention
The present invention relates to an optical device.
2. Description of Related Art
An optical device that adjusts the amount of light to be transmitted by means of electrocapillarity (electrowetting) is proposed (For example, see Japanese Patent Application Publication No. 2001-228307).
Such an optical device 10 includes, as shown in FIG. 12A, a sealed container 16 that includes edge walls 12 that face each other in the direction of the thickness of the container 16 and a side wall 14 that connects both of the edge walls 12, a first liquid 20 having polarity or electrical conductivity that is sealed within the container 16, and a second liquid 22 that is sealed within the container 16 and that has a higher transmissivity than the first liquid 20.
Liquids having such properties that they do not mix with each other are used as the first liquid 20 and the second liquid 22, and further, liquids having the same specific gravity are used as the first liquid 20 and the second liquid 22, so that when only the first liquid 20 and the second liquid 22 are sealed within the container 16 without getting air or the like mixed therein, the initial state in which only the first liquid 20 and the second liquid 22 were sealed within the container 16 is maintained even if the container 16 is rotated or shaken, and a state where an interface 24 is roughly parallel to the edge walls 12 is maintained.
Reference numerals 28 in the drawing is an electrode for applying a voltage across the first liquid 20, and reference numerals 30 is an insulation film covering the electrode 28.
By applying a voltage across the first liquid 20 with the above-mentioned electrode 28, the shape of the interface 24 between the first liquid 20 and the second liquid 22 is altered between the gap shown with the solid line and the broken line in FIG. 12A due to electrocapillarity, and thus, a light transmission path 18 that passes through the edge walls 12 and extends in the direction of the thickness of the container 16 is formed.
Specifically, in a state where no voltage is applied, by having the first liquid 20 extend, as indicated by the solid line in FIG. 12A, over the entire area in a direction that is orthogonal to the direction in which light is transmitted, transmission of light is prevented or suppressed, and as the applied voltage is increased, the transmission path 18 is formed by having the second liquid 22 come into contact with both of the edge walls 12 as indicated by the broken line in FIG. 12A, and the size of the transmission path 18 is adjusted by adjusting the applied voltage, thereby increasing or decreasing the contact area between the second liquid 22 and one of the edge walls 12.